Deflection influence line identification under moving vehicle based on variational modal decomposition and B-spline basis function

Abstract

Bridge influence line has an important application in structural performance evaluation, damage identification, model correction and bridge weigh-in-motion. Influence line identification method based on dynamic testing is often interfered by the vehicle-bridge coupling vibration and the measurement noise. A deflection influence line identification method based on VMD and B-spline basis function was proposed in this article. The VMD was introduced to eliminate the dynamic fluctuation component, and then the quasi-static response could be extracted. The optimal decomposition parameters of VMD were determined by permutation entropy and GWO algorithm. The B-spline basis function was used to expand the influence line, and the identification of influence line was transformed to solve the weight coefficients of the basis function, which would greatly reduce the number of unknown variables and smooth the local fluctuations caused by noise. Finally, the feasibility and accuracy of the proposed method were verified by a numerical simulating and experimental testing, and the influence of various parameters such as vehicle speed, vehicle weight and road roughness were investigated. The results showed that the proposed method could effectively eliminate the fluctuation disturbance, and the deflection influence line could be identified with accuracy acceptable for engineering applications.